1. Field of the Invention
The invention relates to a method for processing binary code words that can be parity controlled, and which, in the course of being transmitted, undergo a digital attenuation and/or code conversion.
2. Description of the Prior Art
Such a method is of interest, for example, in connection with the transmission cf voice/data information in peripheral line groups of digital switching systems in which the binary code words representing the voice and data information are accompanied by a parity bit and, particularly when they are used in connection with conference calls, pass through a circuit arrangement that is designed to generate a digital attenuation, which, if necessary, also effects a code conversion from a code representation corresponding to the A-law to a code representation corresponding to the .mu.-law and vice versa. By means of this latter procedure, the switching system is adapted to the respective country-specific coding that is provided in the telecommunication network in which the switching system is being used. "Attenuation and/or code conversion" implies that the first code words undergo a digital attenuation with an independent code conversion or just a code conversion or both. This will be referred to as a digital conversion.
The generation of a digital attenuation or a code conversion can cause the code words leaving the device that is used to generate such an attenuation and/or code conversion to have a different parity than the corresponding code words prior to such treatment, for which reason a parity bit must be formed afresh for the code words to be transmitted that have been subjected to an attenuation and/or conversion. However, this also means that under certain circumstances parity errors in the incoming code words cannot be detected in the course of code control that takes place at a central location.